To obtain more information about the characteristics of the dye 1-ethyl-2-(3-(1-ethylnaphtho(1,2d)thiazolin-2-ylidene)-2-methylpropenyl) naphtho(1,2d)thiazolium bromide and its interaction with macromolecules. Identification of acidic macromolecules on gels and tissue sections by metachromatic reactions.